Fix a performance regression: Keep two btree masks in each prepared

statement; one for btrees used and another for btrees that require locks.
Only try to lock the btrees identified by the second mask.

FossilOrigin-Name: 614de91a504d2231009a9de1305e31fce1b1c5a6

src/vdbe.c

@@ -4645,8 +4645,6 @@ case OP_ParseSchema: {
     assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
   }
 #endif
-  assert( p->btreeMask == ~(yDbMask)0 );
-
 
   iDb = pOp->p1;
   assert( iDb>=0 && iDb<db->nDb );